A trill is a series of notes that alternate between two frets, and are often Hammer-ons hammered on∞. While the exact musical definition of a trill∞ requires that the two notes in question be adjacent in their scale, this definition applies to any two alternating notes in Guitar Hero and Rock Band. The image to the right shows the trill at the end of the Steely Dan song Song_RB2_Bodhisattva Bodhisattva∞ in Rock Band 2⇒.

Sometimes, musicians can refer to two notes that alternate as trills, despite not being a second (major or minor) above or below a given base note. Such is true in GH/RB, though if a trill is ever notated in music, it always refers to a second above the written note, and if a pattern is considered a trill in any GH/RB game, the most common meaning is two adjacent notes.